<ion-item>
    <ion-label no-margin-bottom>Chapter range: {{rangeValue?.lower}} - {{rangeValue?.upper}}</ion-label>
    <ion-range dualKnobs="true" [(ngModel)]="rangeValue" min="1" [max]="chapters?.length" item-content (ionChange)="rangeUpdate($event.value)"></ion-range>
</ion-item>
<ion-row>
    <ion-col>
        <button block ion-button color="primary" (click)="checkAll()">Check all</button>
    </ion-col>
    <ion-col>
        <button block ion-button color="primary" outline (click)="uncheckAll()">Uncheck all</button>
    </ion-col>
</ion-row>